Since conventional methods for the fabrication of a polysilicon thin film require a high temperatures of more than 650.degree. C., a glass substrate with a softening point of less than 650.degree. C. is not able to be used. In order to avoid diffusion of impurities, it is necessary to use a highly pure quartz glass substrate among glass substrates with a softening point above 650.degree. C.
Recently, a low temperature method using an excimer laser has been intensively researched. In this method, however, only a small area such as 5 mm square is able to be crystallized, so that it is necessary to move the substrate in order to obtain complete crystallization over a large area. When the substrate is moved, nonuniformity of crystallization arises in the boundary region depending upon the moving speed of the substrate, so that it is difficult to uniformly form the polysilicon thin film on a large area.
The present invention is made to resolve the above-mentioned disadvantages of the conventional art, namely, it is an object of the present invention to provide a polysilicon thin film and a low temperature fabrication method thereof in which an inexpensive glass substrate such as a soda glass is used as a substrate.